Authenticated RSS Feeds

I’ve got an internal customer running my WSS RSS feed generator (perhaps Scoble will be next?) and I’ve discovered a common issue with most news aggregators. They don’t handle feeds that require authentication. Windows SharePoint is designed to be a team collaboration tool. Obviously, part of team collaboration is not allowing non-team members access. I checked through the source code to RSS Bandit and discovered that while it handles many HTTP errors, including redirection and moved permanently, it doesn’t handle unauthorized. I was able to add support for credentials via one line of code (request.Credentials = CredentialCache.DefaultCredentials;). Of course, what I want is to try the default credentials first, then pop up a dialog to allow the user to enter alternative credentials. XP provides some of this plumbing, but I’m not sure how much is exposed via BCL.